Vibratory conveyors have long been used for transporting particulate matter. While having many uses, vibratory conveyors have been particularly widely used in the food processing industry where they are typically used to convey dry particulate food product, such as rice, grain and pasta, as well as food product in pouches, along the length of the conveyor pan. In the past, the frames of vibratory conveyors have been made of expensive stainless steel for corrosion resistance and easy cleaning. While corrosion resistant cladding has been used in the past to protect food processing equipment having frames made of mild steel, including conveyors, it is believed that such cladding has not heretofore been used to accurately locate components of a vibratory conveyor.
Vibratory conveyors are constructed with an elongate metal pan carried by leaf springs that extend upwardly from a frame carried by a heavy metal base. The pan is three dimensionally contoured having a recessed flat bed with a sidewall along each side of the bed. Extending outwardly from each sidewall is a flat wing and each wing has a downturned downwardly extending flange. An electromagnetic or electromechanical drive attached to the frame is coupled to the pan to vibrate the pan relative to the base. For food applications, the pan is typically vibrated between about 500 and about 1000 cycles per minute with the direction of pan movement generally parallel to the lengthwise axis of the pan.
In assembly, the base is made by joining together a pair of parallel but spaced apart elongate stainless steel beams with a plurality of transversely extending stainless steel cross braces that extend from one beam to the other beam. These cross braces also serve as spring mounts to which the springs that carry the pan are attached. During assembly, the location of each brace is determined manually relative to one end of the beams in an attempt to locate the brace before one end of each brace end is welded to one beam and the other end of each brace is welded to the other beam. Thereafter, pairs of spaced apart leaf springs are attached to each spring mounting brace with one spring of each pair attached to the brace adjacent one of the beams and the other spring of each pair attached to the brace adjacent the other of the beams.
After attaching the springs, the pan is lifted over the springs such that the springs are positioned underneath the wings, between the sidewalls and downturned flanges, and the location of the springs are manually marked. The location of the springs relative to the pan are manually marked and spring mounting brackets are welded to the pan between the sidewalls and downturned flanges.
When manually locating each of the spring mounts, namely the braces and brackets, the intended goal is to locate the springs accurately (a) relative to a common end of the conveyor, (b) relative to a common horizontal plane, (c) relative to a common vertical plane, and (d) angularly. Unfortunately, because all of these spring mounts are manually located, slight mislocation and misalignment of one or more springs often occurs.
This can result in the springs being at least slightly mislocated angularly, relative to one end of the conveyor, and/or relative to the desired horizontal or vertical plane. As a result, forces encountered during normal conveyor operation can undesirably twist the spring, compress the spring, bend the spring too far in one direction, bend the spring without any load applied to the pan, or pull the spring, all of which can lead to spring fatigue, rough conveyor operation, and spring failure all of which typically necessitates conveyor maintenance. Even worse, because the spring mounts are permanently fixed because they are welded, the mislocation and misalignment can be permanent or remain undetected, typically causing a failed spring's replacement also to fail prematurely resulting in increased warranty costs and significantly increased maintenance expenses over the life of the conveyor. If detected, it is extremely time consuming and expensive to remove a bracket or brace spring mount, re-locate it, and re-weld it.
The drive is mounted on a bracket fixed to the frame and coupled to the pan, typically by at least one leaf-type spring. If the drive is mislocated relative to the frame or pan, it can result in rough operation of the conveyor. Unfortunately, if any of the springs supporting the pan are mislocated or if the drive is mislocated, it can adversely impact the desired relationship between the natural frequency of the pan, the natural frequency of the springs and the natural frequency of the drive quite possibly causing the conveyor to be undesirably excited into resonance during operation. This can lead to such rough conveyor operation that the drive can be damaged, springs can fracture, spring mounts can be torn from the frame and the drive mounting bracket can fail, all of which will leave the conveyor inoperable and require expensive, time consuming maintenance.
What is needed is a vibratory conveyor and method of making the conveyor that accurately locates the spring mounts so that twisting, excessive bending, compressing and pulling of any spring of the conveyor is minimized and preferably substantially completely prevented. What is also needed is a method of making a vibratory conveyor that enables the spring mounts to be quickly and accurately located during assembly without requiring the assemblers to manually locate any spring mount. What is also needed is a conveyor that is not excited into resonance during operation. What is still further needed is a vibratory conveyor and method of assembly that is fast, simple, economical, saves labor, and which results in a conveyor of strong, robust and durable construction.